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PARIS - Hormone replacement therapy (HRT), a contested treatment for post-menopausal women that has already been linked to breast cancer, is also associated with ovarian cancer, a study in The Lancet says.
Women who take HRT are on average 20 percent likelier to develop and die from ovarian cancer compared to women who have never been on this treatment, according to the research.
The evidence comes from a major British investigation into female health, the Million Women Study, covering 1.3 million British women from 1996-2001.
HRT entails taking substitutes for oestrogen or progesterone after natural levels of these key female hormones diminish after menopause.
The idea behind it is to reduce symptoms such as hot flushes and vaginal dryness and boost protection against osteoporosis and heart disease.
The British researchers assessed data from 948,000 post-menopausal women, who had been questioned and later given a follow-up exam some three years later.
Around 30 percent were current HRT users; 20 percent had previously received HRT; and the remaining 50 percent had never taken it.
Across all three groups, a total of 2,273 women developed cancer, and 1,591 died from it.
The increased risk of cancer, though, was shouldered by current HRT users, especially those who had been taking the hormones for at least five years. The risk was largely unchanged by such factors as a smoking habit or past use of oral contraceptives.
Women who had stopped HRT had the same risk level as counterparts who had never taken the treatment.
In a commentary, Steven Narod of the Women's College Research Institute in Toronto, Canada, said the relative risk of 20 percent might be thought of as small, "but enormous numbers of women have been exposed."
In the Million Women Study alone, nearly 500,000 had taken HRT, he pointed out.
Extrapolated across the British population, around 1,000 extra women died from ovarian cancer between 1991 and 2005 because of HRT.
The HRT link with breast cancer surfaced in 2002, prompting many women in the United States to drop the treatment -- a trend that notably coincided with a sharp fall in new breast cancer cases in the US.
The authors of the new study are led by Valerie Beral of the Cancer Research UK Epidemiology Unit in Oxford, Britain. The paper appears in next Saturday's issue of The Lancet.
Beral says HRT's effect should be seen in the context of breast and endometrial (uterine wall) cancer, as well as ovarian cancers. These three types of tumour account for 40 percent of all cancers diagnosed in British women.
"The total incidence of these three cancers in the (Million Women Study) population is 63 percent higher in current users of HRT than never-users," the study notes. - AFP/ra
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